Scottish design nationalist renegade rejected (6)
I believe the answer is:
tartan
'scottish design' is the definition.
(I've seen this before)
'nationalist renegade rejected' is the wordplay.
'nationalist' becomes 'nat' (I have seen 'A nationalist ' mean 'nat' so perhaps 'nationalist' could also mean 'nat').
'renegade' becomes 'rat' (I've seen this before).
'rejected' is a reversal indicator.
'nat'+'rat'='natrat'
'natrat' back-to-front is 'TARTAN'.
(Other definitions for tartan that I've seen before include "Cloth with a crisscross design" , "Scots cloth pattern" , "Highland check pattern" , "dress?" , "Symbol of the Scottish clans." .)